Telephone system



July 9, 1929. R. F. STEHLIK TELEPHONE SYSTEM Original Filed June 4, 1926 '7 Sheets-Sheet 1 q a a c o o 0 o o o Eudglph F ETEhlzk Original Filed June 1926 7 Sheets-Sheet 2 Inuen nP-- Eudul h E 51 51-1111;

July 9, 1929. STEHLIK 1,720,012

TELEPHONE SYSTEM Original Filed June 4, 1926 '7 Sheets-Sheet 4 i HU Fud y 9, 1929- R.- F. STEHLIK 1,720,012

TELEPHONE SYSTEM Original Filed June 4, 1926 7 Sheets-Sheet 5 July 9, 1929 R. r STEHLIK TELEPHONE SYSTEM Original Filed June 4, 1926 '7 Sheets-Sheet 6 1 l i ll I 3 MAL SIQTQHE f[ I Inuen dI Burial 111? SIEhhk July 9; 1929- R. F. STEHLIK 1,720.0121

TELEPHONE SYSTEM Oriinal Filed June 4, 1926 7 She ets-Shet v Patented July 9, 1929.

flfhe present invention: relates to; telephone systems in' gener'ehi bllil'i is concerned I more particularly with; i 5 telephone systems in which arrangenients are :provided to; prevent trunking equipment fro'n'n being tied up unnecessarily; when nit becomes apparent that the ,ettempted connect-ion: cannotbe conipleteCl-h 1' "T 1- As aniexaniplemtrthe kind oi -telephone system above -roster-red jto,re't'erence ismade to-the -following7U-Sr Ba tents: v ;l,212-,908,--GooleyyJun. 16; L911. M s 5 1,319,017, I-Iershey-etalQ, May 24:5 1921.

The-spatents-jdisclose systems-in which the connector switch -is :returned to common use in case the called-lineiis'vbusy the busytone being-sup plied rto the calling; line-from the line switchin: one dis'closurel.andztrorn an operators cord circuit in vthe other. disclo- SuI6-u3 wv "3 i 'fii, :;.*;The 'systeinnto-wvhicli the present inven' tion applied Edi'fi'ersvfromthe systems of the i paitentsuinz severe-L ways. In the. first place,-.appliceni"ssystem is e-multi-ofiice system in whielndireetors are employed for routing: the: callsto the' called otlicesaccording to the most economical trunking alrmanagement, and the means 31 01 controlling the: apparatus that sends back the busy signet to the calling subscriber when abusy or other abnormal condition encountered is located in the directors, which 5 are relatively small in number'thus v effecting: a considerableseving; v a An': object-ofthe invention isthe provision of. suitable arrangements whereby the equipment :for. placing; the busy tone mix-the. calling line may be controllcdover an interoflice. trunk line through an automatic impulse-repeater. t l

-.Another objectuofi the inventionJis the production. of. suitable varrangements Where by the director, \vhichvis ordinarily -freed immediately upon the transmissionf of the 7 last. digit in'the number, is heldiinithecom men use, along Withvthe switchingequipment responsive to the*- enoountering of a; busytrunk group or other abnormal eon- F dition eventhoughthe director has nottuner: emi re, fdrl time; nLINc1 ;'-.AssxG 'B; nema.

' ""mo.,oF'oH-IoAeo, inmno spn CORPORATIONKOEDELAWAEE;

' Applicationfiled llune l, 1926, Serie1 No.- 1 13,614. i ilen'ewed'Sentember20fil92'8."

v v .,i.. nix: n'il" n l R21 reached 'lthestege- 'et which it {normally disconnected and returned t-o-cemmon='usei A further object qt the)inventicn'is to ing prove the system by 'a rra-nging the director to sendwback d-ial tone from-the time" it jis seized: until t-he' lastifd-igit is dialled,'" thus reminding the calling man that i he has not finished dialling in case'he pauses before e isthrough. m: 5-

' The. foregoing 1 objects zind teatures w-i ll be better 1 1inderst6od, and i furtlierifeetures of theinvention! will manifest themselves; upon a vperusuul 0t-thezifollmvingdescrip tion of'the epcration 'ot the equipment shown in. 5 the accompanyi n I drawings 'cornpri sing ElgSu1-8. i i-W inl i I v y In); the drawings, l'Fiigs- 1:3 Show the trunking 'equ-ipmentl necessary to set 111') an inte'r-ofii cei connection 'frornva *finunk com prising: -COIlClUCtO1'su2-4;i to thei=lii1'e of' sdhstation B,' Fig. 3 clihgsi 4+7 shoiw th'e direc= tor thletiis usediintcontrolling the establisli ment-of-a connectierr-endwhizihiisessocizited with i the trunk; circuit TC, 1; through the medium ofithedirector selectolwDSu and Fig. 8 shows a modification of the-selector g ej u Ina Fig. l,- theutnnrk' comprisingwconduef tors may be =ac'eSsiblen-t-o calling-lines through; ordinary lineswitches; end," when the; trunk is seized, the director selector DS operatesto connect up an idle director'.: The triulk line incoin-ingio the-trunlr-circnit-TC is continued -thro1igh-zconductdrs '2- 4" to the oflice selector OS after theioperation jot the switching relay 8,2 which occurs efter'the connection hasiibee'n setlnp-zto the desired line. i-The ofiiceselector 0S =has access on onelevel, as shown fito trunk lines leading to another office end; termineting in thou sends selectors, For example, the trunk line comprising conductors 84- 86- eXtendSto the repeater R, from which ztztwo conductor-fin ter-officeimunk line liszextended'to the second oificetotho thonszinds selector 'DSL" It i's to be understood that v on other levels the ofiice selector OS: may have 'eccess "to thousands selectors; or tovother offiee selectors 'in the seine-orJanother-.-oflice, dependingu on' the size of the system and the particular trunk ingarrangement employed. 1 {HF-11 i3 R-et'errinz new to" Figs. 2 and 3, the: thou sands sel'ettonTS has eccess-on its severel levels to groups of'liundreds selectors, one of WlIiChHSQlECtOIS is the. hundreds selector HS. .The lrun(beds-selector HS; has access to group., c'onnectors, onei-of whlchconnectors is the connector C shown in Fig. 3.

the various switches; shown in Figs. 1-3, the selectors and'the connectorare of the usual vertical and rotary type, having bankvcon- "tacts arranged in ten horizontal levels, and

{the director selector DS is assumed to be of the well known rotary type of switch which is used extensively as subscribersindividual lineswitches. l Referring now to the director shown in Figs. 4-7, the portion of the-director shown in Fig. 4 includes the sequence switch S, whichiis used primarily to distribute the incoming series of impulses to the various operating magnets of the registers shown in Figs. 6 and 7. Fig. 4 shows also the sequenceswitch S which is .used primarily to render effective the various register wipers one'after' another to control'the operation of the sending equipment shown in Fig. 5, and includin'g thesendingswitch SS. F ig. 5' shows in addition to the counting switch CS, the usual pick-up and stop'relays 404iand 405 which. are used to regulate the length of the impulse series in 'conjunc L1,. 11.. 1L1 -..,..'-L,.' ...LLI ..J 1... ..c other; auxiliary fu11ctions.--This drawing shows also the usual release relay 403 and the'associated relays 401 and402= which con trol the regular switch-through operation and'controls the special switch-through operation when an abnormalcondition is encountered. I

Fig. 6 shows the office register OR and the I intermediate distributing 'fra'me I. D. F. The oflice register OR is a two digit switch having ta vertical movement and a rotary movement and it-i'egisters the office digits of the number. The I. D. F. is provided toenable the control exercised in any given setting of the office register OR tobe as signed-at wilL -.Fig. 7 shows the digit registers DR-'1-" DR-4 which register thethousands',":hun= dreds; tens and units digits, respectively, of the called number, and later control thesend ing equipment to retransmit thesedig'its. Assumingnow that the trunk line comprising conductors 2-4 is seized by a lineswitchwhen a subscriber removes his re ceiver to extend a connection to'the line of substation-B, line relay 5 ofthe trunk circuit. TC operates over the calling line when the trunk line is seized. At armature 9, relay 5 closes a circuit for release relay 6, and relay 6operatesan'd places ground on the release trunlnconductor 3 at armature 11 in the usual manner. At armature 12, relay 6 closesa circuit from ground,- through the resting contacts and armatures 15' and 21 through switching relay 32 and stepping magnet 31 of the selector DS iuseries. At

armature 13,:relay 6 connects the test,:wiper 41 as thexzdirector selector DS tothe juncti,0n, of relay 32 and stepping magnet 31 Regarding the mechanical construction of through armature 3 6, and its resting contact andjthe lrfesting'jcontacts and armatnres- 22 and '16.

Assuming that the director upon which the wipers of the director selector DS are standing is idle the 'closing-of the test circuit at armature 13 of relay 6 is without result,-'and switching relay 32 energizes, seizing the-director. If, however, the said director is -busy, aground potential is pres ent ontheitestcontact encountered by test wiper 41,'=and switching relay 32 is short circuited-and does not operate. In this case, the ground potential coming in through the test wiper of the switch operates the stepping magnet 31 in its usual buzzer-like manner, advancing the wipers of the switch DS step-by-step until an idle director is reached. Assuming that the director shown in Figs. 47 are reached through conductors 43-47 isl the-first one found to'be idle, switching relay' 32, being no longer short circuited, energizesi when the wipers 38-42 of the switclrDSai'rive on the bank contacts in which "the said conductors terminate. At

7 hi fl I over which the impulses are subsequently transmitted-to the director; at armature 36 it opens the' test'circuit and places ground on testwiper 4-1; at armature 35 it prepares a circuit-for busy relay 7; and at armatures 33 and'34it connects the conductors 2 and 4 extending to the oflice selector OS through the wipers'38 and-'39 to the outgoing impulse conductors 43 and 44 of the seized director; When this occurs. line relayfil of the office selector'OS energizes over conductors 43 and 44 and through relay 402, Fig; 5. At*ar'mature 71 relay 61 closes a circuit for release relay 62, whereupon relay 62 operates and prepares the switch for operating by grounding the release trunk conductor 3 at armature 72 and by suitably shifting thecombined impulse and release circuit atarmature 73.

"In the-director, relay 402 opens at armature 410 a point in the circuit of relay 401, and release relay 403 energizes over the release trunk conductor 46 responsive to the above-mentioned grounding of the test wiper 41of the=director selector DS by relay 32. Upon operating, relay 403 removes=ground from the'release conductor 319 at armature 411 removes ground from the restoring conduetor 316 at armature 412; and at armature 411 and its working contact prepares a circuit for relay 401; Relay 401 is not operated atrthistime on account'of-the fact that-relay 402 is energized over the control conductors 43 and 44.

- Dial tone current from the-transformer 230, Fig. 4-, now informs the callingsubease-e 2 seriber thatihe maystart toidialthe number. Theleawer tel;- 'nal of the secondary, winding being, ,cennected to battery through I309 and; magnet 602, and the upper terminal is connected-t0 theelower talking conductor overa paththat includesthe lowca acity condenser 25, Fig.'-,l..

' en the calling-subscriber dials the lirst ,ofiice digit inthe vdesired number, line relay 5 .fallsflback av corresponding number of times and each time it does so acireuit is closed from ground through the resting contact and armature l0, armature 37 and its workingicontact, wiper 42 of the director selector BS, the bank contact on which it is s iding, conductor 47, left-h and winding of transformer 320, series relay 30], wiper 309 of the sequence switch S :the bank con- .tact von. which it isv standing, the associated conductor and vertical magnet 502 of the office .reg-isterOR to battery. By the opera.- tion of verticalinagnet 502 :the wipers of the ofiice register OR areraised step-by-step until they stand-o posite the level. of bank contacts correspcn ing to the first ofiice digit in thenumber. a i A a Series relay 301, .Fig. 4:,is energized upon the transmission of the first im pulse to the vertical magnet of theofiice register, and, being slowecting, remains operated throughout theseries ofimpulses. Upon operating, relay3Q1 closes at armature 303 a circuit for the associated sie vwacting relay 302. Relay 3'02 operates and prepares at immature 30% a circuit which is completedat armature 803 when relay 301 subsequently falls back. This circuit includes magnet 305 ot-the sequence switch S, which magnet operates when the circuit is closed-and advances the 'wipers 3G8 and 3090i the sequence switch S one step. ,The CiIGillt is opened afteran inst-ant bygthe falling back of the slowncting relay .30 r p a "When the secondofiice digit is dial-led, the impulses of current transmitted by line relay 5 of the trunk circuit TC traverserthc path above described to wiper 309 of the sequence switch S, but since wiper 399 isnow on its second contach' the impulses are delivered overtheassociated conductor to rotary mag net 501 oftheofiice, register .OR. By the operation of the rotary magnet, the wipers o the office registerOR are rotated stepicy-Ste until the; come into engagement with t 'e set at bank contactscorresponding to the second oihee digit, assumed ;to he the set shown.

. Byflhe above-described action of relays 3G1 and 30 fl Fig. 4g the wipers 308and 309 of the sequence switch S are advanced onother ste at -the end of the rotary movement "of the o ceregister OR. Wiper. 309 shifts the incoming impulse conductor fronrthc rotary magnet of the o'fiice register to the operating magnet of: the digitnregister DE -'71, ig i7, n 'rw p ig-fi lflteennects the interrupter 610 i tetthe-i start z eonduetor .8511: extending, ;to the sendingequrpmentwshcwu in Figs 5; {This,r'esults tin tlie-istartingoof the sendingoperation as. willhe described 50 subsequently. h :1 Q'iUjfl'Zh aj fl/Vhen 1 he first-subscriber digit (the thm1- sands digit); is dialled,. the :irnpulsesmt cur rent iare delivered ;to 1 the operating magnet of theadigit register aDRi-ele the impulses 76 rep resenting the hundreds digit iazr'e ldeliwltiled to the operatingmaqnet z ot Ethe. digit aegis.- ter DIG-12,; .the impulses representing rthie tensdigitare-delivered to theloperating magnet of the digit iregisten E DEL-3 gnand the impulses representing ,theunits .digit aie delivered to itlIQdOPGlfttifig"? magnetwoio'the digit register;DB-:-4- i'lheiresult (is tillat th'e wipers ct these -registersuare set tiniaceordianee with the subseriben HlgltSZdf desired 5 number, it being nndeistoodi-ohrcbm'se that the wipers of the sequence-1switeli)S' ,-'Figfl t, are advanced onenstep "at: hheieridpoifmthe transmission-cf 'ieach ctr hewabovendigits. hat being the ch'se,-avipen309uisinow stahds $9 ing on the seventh, :bar'ilgitzontdtzt;:ivehich'iis dead; and the: wipers E508: and BOQ'Iemain oh their seventh contacts mutt-lithe connection is released Ailso since; :W'i'per EGE -is on a contact, the flow.- of dial 'ttoiie' c ureent td ithh calling line -s'tops,-'nemin.-ding the nailing siili seriher thatfhe has finished diitlliiigi "t" i Returning new]to theopoiiit 'at whieh 'tiie interrupter 3-10, :Fdg's lg iisotbiineeted to'tlre startconductor 31% byithe: WipeESOS of the sequence switch S at the end of theeipei'alliion of the otfice register (DR impirl-ses; a1nder the control of the internhpten littl are transmit ted rover conductor 3M iaind thrbuhh threstinc; contact (and armature l 44:19 toshe-steppingainagnet $24: of -ltlrersending 'tsw-itch S S. Upon ;enei"gizi=ng= in. response/to the, rfinst of these impulses, magnetdfl operates its nis+ socia-ted anmature rand :nieves: the pawl-into engagementwvith th'eeiinextg step the wiperdriving; i'l'tttClIQt wheel; abut" does. not move thewipers 4i25 and -,4"26.i- Als0,1 the sending contacts A23 are opened; butt ithis does not produce tarry? result au this qtime as the "contacts are shunted'gthmugh erma te 1.8 a d: s; exist ng: eqntas 'e ermae We 3 e d i re ireme t i Brea he deenergiz ation of et i lgh thewipers w and 426cm adyanced one step, and ,w per 425 engages a grounded contact plosimg .a- 1?. Circuit 0 r rur w443%:i Atz neeture 2H3 I pick-up relay $04!, Ij'rempyes rthe, shunt .n ,.a euu z the sending co tac s e2 1 a new s n m'e glthese es. re ay 0 and at armature tlfi t opens aipointiign the 1%5 cir it t-r ley see t P ev nt t re av 'f ma iee r ugliietmebmifl and :its .resting contaclg, responsive to the restoration 5 tot the rurmat-ure, {of relay, 4.02. 'ee' let es h s les: en. cheese m s e the switch-through circuit (to be hereinafter described), and; at armature 4165i, Y prepares a locking circuit for stop relay405' and closes a-circuit' through armature 421 and its resting contact, and .over conductor 317 for the stepping magnet 310 of theseq uence switch S Stepping magnet 310*energ'izes preparatory to' advancing the wipers of the sequence switch when-the circuit of the stepping magnet is subsequently opened. 1 The shunt having been removed from around the sending contacts- 423 at'armature 413, each subsequent energization of magnet 424 results in an opening of' the outgoing control circuit including'conductors 43and 44.- It'will be-noted that stop wiper 426 encounters the first" impulse-stop conductor upon the advance of the wipers o'f the sending switch when magnet 424 .falls backafter having produced the first interruptions in the outgoing control circuits. The advance of the sending switch and the production of interruptions in the outgoing control circuit continue in' any case until a grounded='in1 pulse-stop conductorisreached: In this case the single. oflice digit required is the digit1a Accordingly,- the'first' bank "contact 506; 6, in the set-of bank contacts assigned to the instant called office iscross connected on'the L D. F. to the first impulse-stop"conductor. That being the case a. circuit is closed for stop relay 40'1'ov'er the first impulse-stop conductorto terminate the ofiice digit"1.' The circuit :is as follows: Fromgi'ound by way of the distributing :wiper 313 of the-sequence switch-Sflthe first. associated bank contact, the corresponding coiiductor; wiper- 505 of the ofiice register OR,-bankcontact506,the associated I. DfFLjumper, the'first impulsestop conductor, the corresponding contact in the bank of wiper 426, Fig. 5, the said wiper, and stop relay 405 to'battery. "'Upon e'ner gizing over this circuit, relay 405 removes at armature 418 the shunt from around the series relay 402, permitting this relay to ener gize, and replacesthe shunt'around thesendin'g contact 423; closes another point in the circuit of relay 401 at armature 420;" 'at armature 421 opens the circuit of the step ping magnet of the sequence switch S, Fig. 4, and closes a locking circuit for'its'elf; and at armature1419 opens the interrupter circuit extending to magnet"424" of "sending switch -SS and "closes restoring circuit for-"the sendingswitch'by connecting the magnet 424 through the self-'interrilptiiig contacts 422 to therestoring wiper 425. Acc'ordingly,"'the wipers 425 'and 426 are ad vahced to' their normal position by the buzzer like action of magnet 424. When'the normal position is reached, the'circuit' for operating magnet 424 and the circuit for maintaining pick-up relay 404 energized is opened by wiper 425. The result'is that the pick-up and stop relays fallback one after the other{'*to*start the transmission of 'tlre next digit; as will be described subsequently. Responsive to the opening of 'its'ci'rcuit by the stop relay 405, Fig.5,"ma'gnet319 of the sequence-switch S fall's'backand advances 7 the wipers 312 and 313 one ste'pi" Wiper-s13 removes ground from the'first wiperoff-the oilice register OR and places'*groimd;on" the second wiper on the office' registeri Since the oflice codeuised for'calling the instant called ojflice contains only one'di it; thesec ond, third and "fourth positionsot' the sequence switch '8' must be skipped a'utoina'ti cally without any further codddigit being transmitted. I Tliis'is taken care-6f, as usual, by uinperin'g the reinainin bank contacts of the 'oflice' re ister OR "to 5 the skip" confductor' 318. This being the case; the ground 'pote itiatnow eii'tended to the' scond' Wiper of the oiiice register is extended overt-he'sliip conductor 31 8, by'wayof'the self interrupt; ing contacts 311, Fig. 4,to t-he'steppingj mag} net 310111 the sequence switchfS". the usual buzzer like action of the's'tepping net 310, the wipers 312"an d313 are advanced over the second,v thirdand foiiith sets of contacts and ground isfenteiided te th'e wiper of digit register 'DR-l preparatory'td terminating the thousands di 'it'ih' accordance with the setting of the register DR lfl 'VVhen/the slow "acting pick up a id 'stop relays 404 and T405, Fig. '5 have f .1.l1en im ck one after the other. relay 405 'hilling'backircjat =1.rm-. iuu-'e*41.6= ofr'elay 404, theit-ransmis sion ofthe thousands'digit talies pln ccj i'na manner siiniliir to thetraiis'mission oft-he code digit lie'reinbefore tlescribed. Y Inthis case, the termination ofthedigit' is jdtte r mined by these ttingp'f the"digitfirc s DR'-1 and is'efl'c-ctetl uponthc energiza tion of stop relay '405 met-um following circuit: From ground by way of i'hc distributing wiper 313 of the sequence switch S", the fifth associated bank contact, 'the 1 corresponding conductor, wiper 'of'the.digit'register ,DR l, the bank 'contacton which? it is standingithe correspondingimpulse stop conductor, the

tor

sponsivc'to the" opening '01": its locking circuit v corresponding contact in thc 'bank trite sending switch SS, wiper 42G} fan'd stop re] 405 to battery. The energi'z atiohfof ref lay'4Q5 te'rmi'nates,,tl e' digitinthem described hereinbefore the" sending SSlis returnedto o -magma the seqliwqp switch S s advance an'o tl ei step, j g. "'In asirnilar manner, the hi'indr edsgten's and units are tra ns l ittetl gandi are terminated in accordance, ivgthi thesctting of the 1 digit [registers 12E 2, and DR-4, 'rspectitelmltlie iwipers" of the se quence switch S;- be'ing advanced one'step the usual manner at the end of eacliof'the said digits. "'Tliatlbeing'the case. :wiper313 of the sequence switch S groundscondiictor 318 at the end of the transmission cf the is delayed fen-a 'slig mas-e mean 5511161 jdi-i'eetor at 1 thisi j'eii it, pei atid li of "the i tomatic p'ense to j -th'e transmission 0 Etna "silhseriiber digits Wili' now be '"Ki'tterasli ht nter'vai; the slow aeting refalls iiackfanci Completes the rotary ngztgnfetfeii cuit Rotary magnet 68 Ql'lGIT- gizesztndztdvitncesthe associated wipers one ciiit' for stepping My @4 "mid magnet v obens' 16 intei rupter contacts the 'cirenit' of relay 64. Relay falls back "and -opens the rota-ff cuc'uit, wh'e e pqn' the 110- I "and c lqs'esiits inter- 65 energizes in's'e'l i'e's with stepping relay 64, seizing the trfih'kf'lf the trunk is busy,'

however, gr011'hd"pbtentia1 is encountered on ates and closes:fet eifma-tiiieh'76 the "i'etavry, m me-emit again; whereupon the w pers 0t ihefs'ele'cter mre This el minate e emien of stepping rea '68 continues in thisr'nannee-until lain id'ie itiu'nh is reached. Assume 84'- S6. When this idle trunk is reached switching i-elay- '65, being nolonger short circuited, Operates "from gro'iind; on the =1"e;

lees e, 'ti'unk cdnductor 3 and thr bi gh 0H- nor ne l contacts '69 ahcl'the rot aty magnet interrupter contacts, ,and in series with i elaly 64. Relay'ffit does not pere'tefit thi's OS" b'eflire' the slow acting re lezrse re'lztyfifi has had time to fall back, r i "j the thousands digit is transmitted. by the'dir'ector, 1am relay'iOQ of therepeaier R falls back Trioinentaifij e' zxch time an teifruptiehj'is f rodwced in thewuftg'oing 'co j t-Idi', circuit (if "the director. time f t;

operition ef this relay at this time, and zit onta t.

cent-act. flltelayfllor does "not have time to operate at this timelb'eing Slightly slow-toQ "onacc ount of the fact that relay 105 operatesagain and opens the circuit at armature L104.

I YVhen thehuridreds' digit is transmitted thedirector, it is repeated by the repeater R 'in the foregoingmanncr to the hundreds s electo'r Hspwith the result that the 1mm dieds"selector.raises its wipers opposite the correspondingflevel of bank contacts and rotatesthem' ini' s earch of an idle trunkline leading"toafconnector in the desired group. Assuming that the tI'unk'lir e leading to the connector G, Fig;'f'3, and'lcoinpri'sing conduiitdrs2 01' f203 'is the first one found to be idle the hundreds selector HS extends the Qi fiO -P 1 i h CO ifi bPi C That be the case lineielay 209 M the connector Q energizes over conductors 201 and 203., ,At

i and 216.

" number of fill X188. I

loses a circuit for vert cal assaul 217, euyaos closes a circuit for release relay 211. Release relay 211 energrzes and prepares the operating circuit at armatureg220; extendsground to armature 2250f busy relay21 1 at armature 219; and atarmature 218 places ground on release trunlrc'onductor 20250 as to maintain the preceding selectors operated and so as to furnish current, for locking up .relays 213 Whenthe director transmits the 'tens digit in thefnuinber, this digit is repeated at the repeateifllt Will-11.13116. result that line relay 209 ofthe connector C fallsback a corresponding A ,Each time it fallsback, e re ay 2 i 1nagnet 204, the circuitat the time of its first elosurebeing as IE OllOWSZ F1'OIT1 ground byway of ,a1'n1atu1e217 and-its resting contacts, armature .220 and its. working contact, contactof off-normal :spring .207 andsaid spring. series relay 21.2 andvertical; magnet 204 to battery; .By the operation of vertical magnet 204, thewipers 236238 are raised step hysstep untilthey stand-,opposite ,the

desired level of bankcontacts. Series relay 21 2 en rgizes uponwthe first impulse of current andrnaintains itsar'r'nature v221 attract .ed until after the last impulse has-been received. Armature 22 l maintains the cir.-.

cuit ofrelay .212 and vertical. magnet 2041 intact and maintains the rotary-magnet cira cuit open after the off-normal springs have shifted, as a they; do upon the first ,vertical and armature 110 and its working ste 3. At the end of the vertical n oyement,

relay'212 vfalls back and shifts thebperating ti conductor froin the vertical .magnetcircur contact, "resting contact and armature 226,

and armature 234 and its restingcontactlto rotary inagnet 208. Rotary magnet 208fre-j sponds to these ilnpulsesand rotates the wipers 236-238 ontothe bank contacts 239-2 11 of the desired line. fiSlo'w acting relay 215 operates responsive to the first rotary impulse and' remains operated throughout the rotary movement. At armature 228,relay 215 disconnectstest wipe-217 from the upper winding of switching i'elay 216 and connects it instead to the busy relay 21 1, and at armature 229 sh u nts the i'sting contact and armature 226 so as to maintain its own circuit and that of rota'ryinagnet 208 intact regardless o1 anyenergi zationsjof the'husy relay. 214 that may occur du ing the rotary inoveiuent dueto yipeir enj countering busy test contacts." Fofasiiiiila r g reason, arinature 230 shuntsthe restingtpnf: tact and armature 2271 f The operation taking place at the end the rotary movement ofthe connector is derelay 2&12 of theralled line to batteryll Re lays 210 and 21-2 energize ,in series with each othieiyaud relay 2 12 clears the calledline attachuuaus in the usual manner.

In the connector, C, relay 21G lock:

,by passesi ing circuit itself at armature 223'; its test winding at aru'iaturef232; opcns the rotary magnet circuit, at armature 234; and at ai'inatiires 231 and 235 connects up the line, wipers 236 and 238,, whereupon ringing c1112 rent is projected out overf tlie called li ne,

returning. to .hattery through the. upper.

winding oi": the ring cutsofi' relay 213 I Returning now; to the d'reeto1-,.it will recalled that they switching-through circuit.

has been prepared theadv ance of Wiper 313 of the sequence switch. S fonftg its, last bank contact; which isrconnectedg vith con ductor v318, and that switchingthrough: operation is being held. up by,slo,w;act lng,

relay 40 1 to give the connectortime totest the calledline. It will be recalledalso that the circuitof relay 404is opened uponeach r'etnriito no'rnial of the sending switch SS, whichireturnto normal is-initiated upon the energizationof stop relay 405 at'the end of each (ligitirflhat-being the' case relay 104: .5; falls back at the end of theinterval for which iii-is adjusted-and at'armature 417 connects the grounded conductor 318 with conductor 17, thereby closinga circuit through wiper 42- ot the: director selector DS, working contact a-nd'armature 37, and armature '10 and its 5 working contact. :for the switching relay 8;: Relay Senerg'zaes-over this circuit and closesiat armature -a. locking circuit for itself fromthegrounded release trunk conductor 3; opensa further point in the test circuit of the director selector DS at armature 22; at armature 21 opensthe circuit ot switching relay 32; joins the release trunk conductor-s3 and 3 at. armature 19; and at :armatures 18 and disconnects the incomingconductors 2 and 1 from the windings of relay 5 and extends them to the corresponding conductors 2 and 4" extending to the ottice -.selector OS. Relay 32 ot the director :sel'cctor DS now falls back responsive to the opening of its circuit at armature 21 and frees-the director, leaving the maintainance oi the established connection under the direct control. of the calling line.

[In thedircctor, relays 4-02 and 403 fall back when vthe director is freed, and relay st. opens at. armature 411 a point in the circuitol relay 101 and-places ground on release conductor Elli), at ground on the rcstoring conductor 316 of the sequence switch-S at. armature 411.2. This latter operation results in the automatic movement of the wipers 1312 and 31?; ot the switch S- through the remaining step totheir normal position, magnet 310 of the switch S being operated through wiper 312 and through its salt interruptingcontacts 311. Responsive to, the grounding of conductor 3119, release magnet 306 of the sequence switch S energizes throngh oil-normal contacts 307 release magnetiitlll oi theotiice register OR energizes through oft-normal contacts 504, and the release magnets of the registers shown in Fig. 7 energize through their respective fifl associated oil-normal contacts. -The result that all those switches are restored to their normal. position in the usual manner. The

restoration to normal of thesequence-switch 308 the-start circuit so that S opens at wiper the sending switch SS another operation of is not. started when the slow back. -5

-Wheirthe called subscriber responds to the ringing. of his hell by removing his receiver,

'the transmitter bridge is substituted for the ringer circuit. resulting in the operation of ring'cut-otli relay 213 of the connector C At armature 2223 relay grounded release trunk conductor 202; and

"atarmaturcs- 2 22 and 224 it disconnects the the same time placing relay 105 stalls 213 looks itself to the relay 209 is disconnected from oonductor' 203. Accordingly, line relay- 209 and *relay wipers 236 anti/238 'itrom its own upper and completes mrtter current now mitter at the called station. The calling and called subscribers may now converse;

with each other in the usual manner.

\Vhen the conversation 18 over, the two subscribers replace their receivers, and when the receiver is replaced at the calling substation, line relay 102 of the repeater E, Fig. 2, falls back and, opens the bridge across the associated trunk at armatiire 108', andat armature 10'? opens the circuit of release relay 103. Release relay 103 falls back after a slight interval and removes ground at'armature 109 from therelease trunk conductor There is an incidental operation of relay 1.04 which prevents the operation of relay" 101-a'tter the falling back otrelay 105 and prior to the falling back ott relay 103.

Responsive to the removal of ground from the release trunk conductor 85, switching relay 65 of the office select-0r OS and relay 8 of the release magnet circuit at armature 220 through the oft-normal contacts %6. The

operation of release magnet 205 results in the usualrelease ofthe connector C. Relays 213 and 216 ot the connector fall back re .sponsive tothe removal of ground from the release trunk conductor; The intermediate selectors TS and HS both release in a manner similar to that described'in connection with the otlice selector GS, Fig. 1'.

It will be assumed nowthat the line of substation B is busy when called as herein before described. In this case, busy relay 214 is energized when the'wipers land on the bank contacts ofthe called line, and a lockin; circuit is closed for relay 21l'upon thef the trunk circuit both fall back. Switching relay- 65 closes at armature 79 a circuit through armature 71 and its restingfalling backof relay1'25; This loclcing circuit includes armature 225 and its working contact, and the normally "closed contacts controlled by armature 228. lVith relay 2% locked energized, and with 'rela-y- 215'ina restored condition, the lower winding er 105;ofthe repea'tera R'both fall back.

lease u-elay .Zlliand. closes apoint in the op erating. cincuit,,but this circuit is open at armature 226,- ;of. busy relay 21 i.v

In E the repeater, relay; v105 closes at arma-,

Inthedirector,relay 402 closes armature 410 thecircuit ofrelay 401. Relay illl at armature 409. placesground; on conductor 45, thereby closing a circuit through wiper 100f the director selector DS, and the working contactand -armature,35, for relay 7. Relay Zenergizes and leeks itself at armature l4,at the same time opening the test and :holding circuits of tlijeadirector selector DS at armatures'lti and 15. Accordingly, relay 32 ,oi'l the director selector DS falls back. and frees, the'director, wh ich restored to.,nor mal;in theusual; manner. As a turther result .of its operation, relay 7 at armaturel? ,connects-the lead coming from the busysignaling transformer 24 tothe-alowcr talkingconductor 4! through the iresti ug con- The calllng suhscrib-- {QI'J liearsithe ,busy signaling tone, and is intact and armature 23.

formed thereby thatthe desiredv connection cannot he.conipleteditorthe timelheing.

-In. .the CQnneet-o1.C, chigfl 3,. release relay 211 falls backkafteinan intervaland closes the release: magnet I circuit at. armature 220, atthe same-time opening the lockin circuit of relay; 214, at armature 219. i, The connector is restoredin :theusual manner.

,ln the'repeater R, release .relay- 103 falls backgafter an interval and opens-thecii'rzuit of relay .101 iat armature 110, ungrounds the relfisetrunlr conductor ,85 at armature 109,

whereupon;,tl1e,,o1iice..selector. OS, Fig. 1,:

releases. i i

connectionwith -the-icalled line isnow re turned to common use; i i

It may be pointed out-that, If: des1red,a

conductors 2,'-3Qand- 4:, .in which ease the otiice selector US would be returned lo com- 'relay 5=fallsback andnopenstlie circuit of Relay- 209lopens-rthecircuit of the slow, acting re-- the slow-acting'release relay 6. Relay 6' falls back after an interval and removes ground from the release trunk conductor 3, whereupon relay/Z falls back and the cal-l ing line-switch releases.

Assuming now that the office selector OS, having been directed to a certain trunk group by the director shown in Figs. 47, rotates its -wipers in search of an idle trunk, but is unable to find an idle trunk owing to the fact that all the trunks in the selected level are busy,- the wipers 8l83 are driven beyond the last set of bank contacts. In this case the rotary movement stops owing to the fact. that no ground potenlial is encountered by wiper 82 after it leaves the last test contact. Accordingly, relay 65 operates in the hereinbetore described manner to switch the incoming conductors 3 and 4 through to the wipers 81 and 83. \Vhen this occurs, relay 4:02 in the director falls back, followed by the operation of relay 401, which relay closes the above described circuit at armature 409 for relay 7 in the trunk circuit TC. .The energization of relay 7 results in the director being freed in the hereinbefore described manner, and in the busy tone be ing transmitted back to the calling line.

A moment later, release relay 62 falls back and removes ground from conductor 3, whereupon relay .65 1a] ls back and closes the usual release magnet circuit. The switch is then restored to its normal position in the usual manner.

It will be understood of course that substantially the same operation takes place in 1 case an open trunk is found by the oiiice circuit of relay 401 when the selector switches through upon finding the open trunk, resulting in the operation of relay 7, Fig. l, as before described. It the line conductors are" both closed, however, and the open trunk is one in which the release trunk conductor for exam ple,'the release trunk conductor 85 of the repeater- R) is open, relay I 402 does not fall back. When relay 62 falls .-.It;w1ll ;thus be-noted that allot the trunlcing equipment beyond the ofiice selector ()S I that was involyedyin the attempt. to make back, relay (55 of the selector falls back and closestherelease magnet circuit, at the same I time again connecting up line relay 6L l'Vhether or not the selector releases at this time depends upon the relative adjustment of the-release magnet'and the line relay. secondary lmnlung switch of r any suitable type ,couldbe inserted between 'the trunk circuit .TC andthe ofiiceselector ,OS in the 'release magnetcircuit at armature 71,- because the release magnet has-had time to operate, and the-release and switching relays energize again one after the other, after which the line relay falls back, followed by the'falling back 'of the release relay and the :switching relay again. This operation keeps up until the usual switch-through operation of the director is performed and relay 8 of the trunk circuit TO pulls up and switches the connection through. Then after relay 6 has fallen back, the holding up of the calling lineswitch and the continued energization of relay 8 are dependent upon ground supplied over the release trunk conductor 3, and since the ground is intermittently removed due to the. above described fluttering action of relay (i2, relay 8 falls back again and the calling lines-witch and the switch OS release, and the lineswitch seizes thetrunk circuit TO anew. The director selcctor operates again as in a new call picks out. the same or another director, and the circuits remain in this condition until the calling subscriber either dials again or replaces his receiver.

If so desired, the selector OS, Fig. 1 may be replaced by the selector OS, Fig. 8, in which case the operation is the same as before except that the open condition is relayed back over the talking conductors to the director when anopen trunk is encountered in which the release trunk conductor only is open, as will be described hereinafter.

A comparison of the selector OS, Fig. l, and the selector OS, Fig. 8, reveals that the selector OS is substantially the same as the selector OS with the exception of the addition of armatures 9l95 together with the associated circuit changes. The parts in Fig. 8 that are the same as in Fig. 1 have been given the same reference characters exce 'it that the reference characters are primed in Fig. 8. Considering the dill l'erences in detail, it will be noted. that ground is connected directly to armature 71', Fig. 8, instead of through armature T9 and its resting contact. This is done so as to permit relay 63 to operate again when the selector switches through, and it necessitates that the vertical magnet 67 be cut-ofl' at armature 94: of relay 6,5, and that armature 79. opens the circuit of the release magnet 06.

As a result of the above changes, a new operation of relay 63 is secured but the remainder of operation of the selector is unchanged. hen line relay 61 falls back responsive to the operation of relay 65 it closes at armature 71 a circuit through armature 73 for relay (3". Relay 63' opcrates and at armature 92 removes the shunt from around armature 91 and its working cont-act. A moment later relay 62 falls back and removes ground from the circuit of switching relay 65 at armature 72' and at arn'iature 91 disconnects the upper winding of relay 61 from the resting contact of armature 77'. Ordinarily this operation has no immediate effect and the connection remains established. Assuming, however.

that the release trunk conductor of the seized trunk is open, no ground potential issupplied to maintain relay 65 operated after relay 62 falls back, the restoration of relay 62 is followed by the restoration of relay 65. At armatures 77 and 80, the conductors 2 and 4 are again connected to leads extending to windings of line relay 61. Now, since the upper lead is disconnected at armatures 91 and 92' from the upper winding of relay 61, relay 402, Fig. 5, falls back, resulting in the operation of relay 401 and in the consequent operation of relay 7, Fi 1, to give the calling subscriber the usual busy tone and to free the director. The release magnet circuit of the selector OS is closed at armature 79 upon the falling back of relay 65, and the switch is restored to its normal position in the usual manner. A moment later relay 63 falls back and reconnects the upper winding of the line re-' lay to the resting contact of armature 77.

It will be understood of course that the selectors TS and HS, Fig. 2, may be the same as the selector OS, and that the holding ground supplied by armature 93 of relay 63 is of utility in holding'up the selector TS momentarily when the selector HS encounters a trunk having an open release trunk conductor. It will be understood further of course, that the encountering of a busy trunk group by the selector TS or by the selector HS produces an effect similar to the encountering of an open trunk, and that this condition is relayed back by the repeater R to the director handling the connection, with the result that the calling subscriber is given the busy signal and the director is freed in the manner hereinbefore described.

lVhat is claimed is:

1.. In a telephone system, a plurality of lines, a director common to all said lines, automatic switches, means for connecting said director to one of said lines and for operating a train of said automatic switches under the control of said director to set up a connection to a called line, and means in said director controlled over the established connection responsive to a busy condition of the called line for causing said director to be freed.

2. In a telephone system, a plurality of lines, a director common to all said lines, automatic switches, means for connecting said director to one of said lines and for operating a train of said automatic switches under the control of said director to set up a connection to a called line, and means in said director controlled over the established connection responsive to a busy condition of the called line for causing said train of switches to be released.

3. In a telephone system, a )lurality of lines, a director common to all said lines.

automatic switches, means for connecting said director to one of said lines and for operating a train of said automatic switches under the control of said director to set up a connection to a called line, and means in said director controlled over the established connection responsive to a busy condition of the called line for causing said director to be freed and for causing said train of switches to be released.

4. In a telephone system, a plurality of lines, a director common to all said lines, automatic switches, means for connecting said direct-or to one of said lines and for operating a train of said automatic switches under the control of said director to set up a connection to a called line, and means in said director controlled over the established connection responsive to a busy condition of the called line for causing the calling subscriber to be given a distinctive tone indicative of the busy condition.

5. In a telephone system, a trunk line, subscribers lines, means for connecting a calling one of said lines to said trunk line, automatic switches, an impulse repeater, means controlled by the calling party for transmitting impulses to said repeater to operate said automatic switches to set up a connection to a called line, means responsive to a busy condition of the called line for placing a special condition on said repeater, and means in said trunk line responsive to said special condition in said repeater for bringing about the release of said automatic switches.

(3. In a telephone system, a trunk line, subscribers lines, means for connecting a calling one of said lines to said trunk line, automatic switches, an impulse repeater, means controlled by the calling party for transmitting impulses to said repeater to operate said automatic switches to set up a connection to a called line, means responsive to a busy condition of the called line for placing a special condition on said repeater, and means in said trunk line responsive to said. special condition in said repeater for bringing about the placing of a busy tone on the calling line.

7. In a telephone system, a trunk line, subscribers lines, means for connecting a calling one of said lines to said trunk line, automatic switches, an impulse repeater, means controlled by the calling party for transmitting impulses to said repeater to operate said automatic switches to set up a connection to a called line, means responsive to a busy condition of thecalled line for placing a special condition on said repeater, and means in said trunk line responsive to said special condition in said reneater for bringing about the release of said automatic switches and for placing a busy tone on the calling line.

8. I11 a telephone system, a line, a sender,

automatic switches, means for connecting said sender to said line and for operating a train of said automatic switches under the control of said sender to set up a connection to a called line, a control circuit extending from said sender and closed when the sender is connected to said line, the said control of said automatic switches being effected by interruptions produced in said control circuit by said sender, means for interrupting said control circuit in case an abnormal condition is encountered in the setting up of said connection, and means controlled from said sender responsive to the lastnamed interruption of said control circuit. for giving the calling subscriber a busy signal.

9. In a telephone system, a line, a sender, automatic switches, means for connecting said sender to said line and for operating a train of autonjiatic switches under the control of said sender to set up a connect ion to a called line, a control circuit extending from said sender and closed when the sender is connected to said line, the said control of said automatic switches being effected by interruptions produced in said control circuit by said sender, means for interrupting said control circuit in case an abnormal condition is encountered in the setting up of said connection, means controlled from said sender responsive to the last named interruption of said control circuit for giving the calling subscriber a busy signal, and means for pre venting the last named means from responding to the said interruptions produced in said control circuit by the sender.

10. In a telephone system, a plurality of lines, a director common to all said lines, automatic switches, means for connecting said director to one of said lines and for operating a train of said automatic switches under the control of said director to set up a connection to a called line, means for freeing said director after the last automatic switch has been operated, means for delaying the freeing of the director until the last named automatic switch has tested the called line, means in the director controlled from the last named switch it the called line is busy, and means in the line to which the director is connected and responsive to said means in the director for placing a busy tone to the last named line and for releasing said switches.

11. In a telephone system, an automatic switch having access to trunk lines, talking conductors incoming to said switch, means for producing a current flow in said conductors and for interrupting said flow to operate said switch, and means in said switch for producing a substantial interruption in said current flow responsive to an open condition of the test conductor of any seized trunk.

12. In a telephone system, means including two automatic switches in serial relation for ii rst switch.

switches for setting :up connections, a" 'ditest conductor tot pi'odncin sweetie i 1 setting up' a connection tea trunk line' acces'sible to the second sw' ch're 'sponsiveto current-flow interruptio s in the talking conductors incoming to said 'switches,means in the second "witch fortl'ioltling' the first switch operated beta-1e the, trtniligline' .is seized, a holding conductor at tlte trunk line for holding both switches oo'erat etl after-"the 'trunk lineis 'sei'liethia n'd means ini'sa'id switch for in'terrnpting the current flow n 'thfe talliing conductors incoming to the second switch responsive to an op'en'eontlition'of thfe holding conductor of said trnnklii 'e andl'for holding the first switch operated at the same time so that the current new is also' inter rupte'd in the eontliicto'rs incoi'ning tojth'e telephone "system, alitoini v 13'. In a rector for controlling said witches, mea s in said director for performing characteristic switching operation a switch which is being controlled selects a trunk line having an open talking eonductorfan'd means in one of said switches responsive to the selection of a trunk line having an open D an artificial in the trunk line inopen circuit condition coming to such, switch 'oitdei" to Babette the. said switching means in said director.

14. In a telephone system in which conncctions are setup responsive to successive operations of a calling device, means for giving the calling party a distinctive signal informing him that he may now operate his calling device and for giving him said signal again in case he stops operating his calling device before he has turned it a suliicicnt number of times.

15. In a telephone system in which conncctions are set up responsive to successive operations of a calling device, means for giving the calling subscriber a continuous signal until he has operated his calling device a sufiicient number of times.

16. In a telephone system in which con nections are set up responsive to successive operations of a calling device, means for giving the calling subscriber asignal and for removing it responsive to the last oper ation of the calling device.

17. In a telephone system, means including a register sender for operating a train of automatic switches to set up a connection to a desired line, and means in said register sender controlled through said train of switches responsive to a busy condition of the called line for causing a busy tone to be placed on the calling line.

18. In a telephone system, means including a register sender for operating a train of automatic switches to set up a connection to a desired line, means in said register sender controlled through said train of switches responsive to a busy condition of i of irate realise, an me'ans' controlled iii-aeby. calling party over the cfall ng,}lin-e 'ofthe busy condition of the .e'anea'iiaeg" "j f "lgfflii f afteleplione'systen1, inca-ns includal aregister-sender for operating a train aatdmatieskvirehes to. sct np a connection in) a desired tint, and means in said register s'entl'ei controlled"through said train of swvitcliesWesponsiife' to it busy condition of the calledlin'e for causing said train of automatic switches to be released.

20. In a telephone system, means includregi'ste'nsender for operating a. train of automatic"switches to set up a connection 't'oa "desired line,1neansjin said register s'ende'ri dean-0110a through said train of switc'l'ie s responsive to"a busy condition of the icall-eil'l'ine' and means controlled thereby for? releasing said train of automatic switches and for informing the calling party over the' callin'g' line of the busy condition oi the earned-ante; i

"' 21;"Ina-ltelephone system wherein co'nneenans'jare setup from acalling line to it called nae through a trunk line by means of"a*"tiai' o't auton'iaticswitches, a controllii new common to said trunk line avian-ea pl urality of similar trunk lines and arranged to be temporarily connected' with any one of said trunk lines, and means including means in said common controlling device responsive to a busy condition of a desired line for placing a busy condition on the calling line.

22. In a telephone system wherein cou nections are set up from a calling line to a called line through a trunk line by means of a train of automatic switches, a controlling device common to said trunk line and to a plurality of similar trunk lines and arranged to be temporarily connected with any one of said trunk lines, and means in said common controlling device responsive to a busy condition of a desired line for causing the release of said train of automatic switches.

23. In a telephone system wherein connections are set up from a calling line to a called line through a trunk line by means of a train of automatic switches. a controlling device common to said trunk line and to a plurality of similar trunk lines and arranged to be ten'i 'iorarily connected with any one of said trunk lines, and means in said common controlling device responsive to a busy condition of a desired line, and means controlled thereby for releasing said train of automatic switches, and for causing a busy tone to be applied to the calling line.

24. In a telephone system wherein connections from calling lines are extended by antomatic switching apparatus to trunk lines and are extended from such trunk lines to called lines by way of other automatic switching apparatus, means including busy signalling apparatus individual to each of said trunk lines for informing the calling party of a busy condition, a controlling device common to all of said trunk lines and arranged to be temporarily connected to any one of them, and means in said controlling device responsive to a busy condition of a line to which a connection is attempted over a trunk line to which it is temporarily connected for causing the busy signalling means individual to such trunk line to become effective.

25. In a telephone system wherein connections from calling lines are extended by automatic switching apparatus to trunk lines and are extended from such trunk lines to called lines by way of other automatic switching apparatus, means including busy signalling apparatus individual to each of said trunk lines for informing the calling party of a busy condition, a controlling device common to all of said trunk lines and arranged to be temporarily connected to any one of them, means in said controlling device responsive to a busy condition of a line to which a connection is attempted over a trunk line to which it is temporarily connected for breaking down the attempted connection. 1

26. Ina telephone system, a repeater arranged to control the operation of automatic switches over an inter-ofiice trunkline, said repeater having a pair of incoming talking conductors, a source of transmitter supply current connected to said talking conductors through a repeating relay, a pair of outgoing talking conductors having a relay connected in a bridge thereof, contacts on said repeating relay included in said brid e, the

arrangement being such that when the repeater is included in a connection the repeating relay is energized over the incoming conductor andthe bridge across the outgoing conductors is closed by .the contacts of the repeating. rela ,so that the relay connected in the bric ge of the outgoing conductors is operated, circuit connections con trolled by the relay in 'said bridge in case the current supply to the outgoing talking conductors is interrupted outside of said repeater for interrupting current flow over the .incoming conductors, and means for preventing the last named interruption when the current flow through said bridge is interrupted by the impulse relay during the normal functioning of the repeater.

In Witness whereof, I hereunto subscribe my name this 1st da of June, A. D., 1926. RUD LPH F. STEHLIK. 

